I don't know about Cara Pils (Dextrine) Malt, but Crystal Malt has
no enzymes (they have been killed by the heat used in manufacturing
the malt), so there is no point in mashing Crystal Malt. Anytime you
raise the temperature of the malt above 160F or so, you denature the
enzymes that convert the starches to complex sugars to simple sugars.
I simply steep the Crystal Malt in a grain bag while the liquor comes
to a boil. Then I sparge with ice cold water into the primary --
yes, I know it's not as efficient as a hot sparge, but once I pour
the hot wort into the cold sparge water, I can pitch immediately.